According to the “iron triangle,” a product or service can be good, cheap, or fast—but you can only pick two.

That’s why a unicorn inhabits the center of this Venn diagram.

As engineers and architects focused on restoration and renewal, we think the iron triangle is better characterized as an exercise in informed compromise among a variety of factors—through which we can get close to the unicorn.

Take, for example, a re-roofing and insulation project:

“Fast” may be the simplest to define. But is it measured solely in installation time, or the total time from inception to completion, including waiting for delivery of materials, availability of contractor’s crew, etc.?

“Cheap” also seems straightforward. But does it include first cost only, or do we consider maintenance and replacement costs? A 30-year roof might be a better overall value than a 10-year roof with a lower first cost.

There’s no simple definition for “Good.” Rather, it depends on numerous factors: the square footage to be covered, pitch to drain, height of existing parapets, environmental exposure, energy efficiency, emission of VOCs during installation, intensity of foot traffic, overburden or vegetation, and number of penetrations. Perhaps you can think of others.

On some complicated roofing projects with numerous inputs, we've used multiple roofing systems to capitalize on the quality, cost, and schedule strengths of each, coming as close to the triple-play unicorn as we can.